The present invention relates generally to fuel pumps for vehicles and, more particularly, to multi-stage internal gear/turbine fuel pump for a vehicle.
It is known to provide a fuel tank in a vehicle to hold fuel to be used by an engine of the vehicle. It is also known to provide a fuel pump to pump fuel from the fuel tank to the engine. Examples of such fuel pumps are mechanically or electrically driven piston pumps, turbine pumps, roller vane pumps, progressive cavity pumps, gear pumps and mechanically, electrically or hydraulically driven diaphragm pumps.
Some of the pumps used in systems for direct injection of volatile fluids such as gasoline are cam driven or crankshaft/connecting rod mechanism pumps. These pumps require a driving shaft and dynamic seals to prevent fuel leakage outside a pump housing or fuel to penetrate into a lubricated driving mechanism area. These pumps also require a shaft coupling a pump driving shaft with a source of rotational movement (e.g., engine crankshaft, camshaft). Some of these driving sources impose a specific location for the pump in the engine compartment. Dynamic sealing systems are usually expensive and do not guarantee an extensive leak free working life that meets fuel emission and safety requirements for modern engines. Engine driven pumps for direct injection systems also require an additional lift or prime pump to supply fuel from the fuel tank to the engine driven pump thereby increasing system cost. Pumps that are engine driven also have difficulty achieving pressure during vehicle starting conditions since rotational speed is typically below ideal pump speed, thus resulting in starts under less than ideal conditions. This could lead to degraded start performance and higher emissions. Further, piston type engine drive pumps typically utilize drain and re-circulation lines to contain leak and dissipate heat, respectively, adding to cost and complexity.
Known fuel pumps such as gerotor, turbine, and rollervane are able to operate up to about one (1) MPa of discharge pressure. That is not sufficient to satisfy the requirements of a high-pressure PFI or low-pressure Gasoline Direct Injection Fuel System which may need up to three (3) Mpa.
In the case of existing gerotor pumps, of the type used in automotive applications, ability to operate at higher pressure on low viscosity gasoline fuel is limited by internal leakage and high friction causing loss of volumetric efficiency and requiring high power consumption, respectively. Additionally, high friction can cause pump durability and noise concerns. In automotive type gerotor fuel pumps, where an inner gear is the driven member, high friction results as pressure is increased and the inner and outer gears are forced against the axle and housing, respectively. Additionally, higher friction also results as the pressure forces the inner gear against a plate member.
With existing gerotor type fuel pumps, it is typical that the pumping section is separated from the motor section, the pump section being assembled on an extension of the shaft, making the assembly less compact. The shaft drives the pumping section through a driver, in the case of the gerotor pump, the inner gear being the shaft driven element. The drive shaft, to improve volumetric efficiency, may require some type of dynamic sealing, especially at higher outlet pressure, to prevent high leakage along the shaft back into the inlet area. Also, the driving shaft may need guiding to prevent vibrations and bending of the cantilever/driver section of the shaft, phenomena that might induce the failure of the pump in absence of a precise guiding feature. But tight guiding/sealing around the driving shaft could produce high wear at elevated discharge pressure, that also can end in failure of the pump, unless expensive wear resistant materials are used for shaft, guiding and sealing systems.
For medium pressure application, such as gasoline direct injection operating at about three (3) Mpa, attempts to use electrically driven single-stage internal gear pumps usually results in low efficiency-high power requirements. High leakage between gear teeth and gear faces reduces efficiency at high operating pressure necessitating the need for very tight tolerances. Tight tolerances usually result in high costs and poor durability.
Therefore, it is desirable to provide a fuel pump by a combination of a turbine fuel supply module and an outer-gear driven gerotor fuel supply module, integrated with a brushless electrical motor and motor controller in a compact and robust design for a vehicle. It is also desirable to provide a fuel pump for a vehicle by providing a medium pressure fuel pump by combination of a turbine fuel supply module and an outer-gear driven gerotor fuel supply module, integrated with a brushless electrical motor and motor controller in a compact and robust design, to satisfy the requirements of a medium-pressure fuel delivery system. It is desirable to provide a pump that can be used for pumping volatile or non-volatile fluids for a vehicle. It is also desirable to provide a fuel pump that has an electrical driving mechanism contained within a common housing, eliminating the need for additional prime or lift pumps. It is further desirable to provide a fuel pump that eliminates any source of fluid leak for a vehicle and is able to provide adequate flow at desired pressure during vehicle starting conditions. Additionally, it is desirable to provide a pump that can be mounted either in a fuel line or fuel tank. It is still further desirable to provide a pump not requiring drain or re-circulating lines. It is also desirable to provide a pump that can be modular in design so that pumping sections can be added to reduce sectional pressure differential and provide for operation at higher pressure and efficiency at nominal tolerance levels.
It is, therefore, one object of the present invention to provide a multi-stage internal gear/turbine fuel pump combined with a turbine or other type of supply fuel pump module for a fuel tank or for xe2x80x9cin-linexe2x80x9d mounting in a vehicle.
It is another object of the present invention to provide a multi-stage internal gear/turbine fuel pump for a vehicle that provides a driving mechanism completely contained within a pump housing.
It is yet another object of the present invention to provide a multi-stage internal gear/turbine fuel pump for a vehicle that provides high discharge fuel pressure to satisfy requirements of a medium pressure gasoline direct injection fuel system pressure that can not be generated by a single-stage internal gear pump.
To achieve the foregoing objects, the present invention is a multi-stage internal gear/turbine fuel pump for a vehicle including a housing having an inlet and an outlet and a motor disposed in the housing. The multi-stage internal gear/turbine fuel pump also includes a stationary shaft extending axially and disposed in the housing. The multi-stage internal gear/turbine fuel pump further includes a plurality of pumping modules disposed axially along the shaft. One of the pumping modules is a turbine pumping module and another of the pumping modules is a gerotor pumping module for rotation by the motor to pump fuel from the inlet to the outlet.
One advantage of the present invention is that a multi-stage internal gear/turbine fuel pump is provided for a vehicle. Another advantage of the present invention is that the multi-stage internal gear/turbine fuel pump is low cost, simple construction and eliminates the need for expensive dynamic shaft seals. Yet another advantage of the present invention is that the multi-stage internal gear/turbine fuel pump eliminates the need for mechanical coupling with a driving device. Still another advantage of the present invention is that the multi-stage internal gear/turbine fuel pump can be placed in the fuel line near the fuel tank or located in the fuel tank. A further advantage of the present invention is that the multi-stage internal gear/turbine fuel pump incorporates a high speed DC electrical motor, allowing for a quick priming of the pump and fast pressure/flow generating and eliminating the need for lift or prime pumps. Yet a further advantage of the present invention is that the multi-stage internal gear/turbine fuel pump is compact, modular and easy to assemble. Still a further advantage of the present invention is that the multi-stage internal gear/turbine fuel pump incorporates a plurality of modular gear pumping modules, allowing output pressure to be increased to a required value of direct injection fuel systems. Another advantage of the present invention is that the multi-stage internal gear/turbine fuel pump incorporates integral pressure regulation or pressure by feedback-speed control which simplifies the system to a single line supply typically called return-less or demand supply.
Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.